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A. T. DAWSON AND G. T. BUCKHAM.

SIGHTING APPARATUS FOR ORDNANCE.

APPLICATION FILED JUNE 22. I915.

Patented June 10, 1919.

2 SHEETS-SHEET ms PETERS co Pno1n l mo. \vnsmmzm A. T. DAWSON AND G. T. BUCKHAM.

SIGHTING APPARATUS FOR OBDNANCE. APPLICATION FILED JUNE 22. 1915.

1,306,41 2 Patented June 10, 1919.

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UNITED STATES PATENT OFFICE.

ARTHUR TREVOR DAWSON AND GEORGE THOMAS BUCKHAI VI, OF WESTMINSTER, LONDON, ENGLAND, ASSIGNORS TO VICKERS LIMITED, OF WESTMINSTER,

ENGLAND.

SIGHTING APPARATUS FOR ORDNANGE.

Specification of Letters Patent.

Patented June 10, 1919.

Application filed June 22, 1915. Serial No. 35,729.'

To all whom it may concern.

Be it known that we, Sir ARTHUR T. DAW- SON, knight, and GEORGE T. BUCKHAM, both subjects of the King of Great Britain, and residing at and whose post-office addresses are Vickers House, Broadway, W'estminster, county of London, England, have invented certain new and useful Improvements in and Relating to Sighting Apparatus for Ordnance; and we do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertains to make and use the same.

In connection with ordnance sighting apparatus, it is usual to provide means whereby, when the trunnions of a gun are inclined to the horizontal as a result of the gun carriage resting on uneven ground, the sight will be deflected to compensate for the lateral error which would otherwise occur. In addition to this error there is however a further error which as is well understood afi'ects the laying of the gun for range, this error resulting from the fact that the angle between the axis of the gun and the sight linee'. 6., the angle of tangent elevationwhen projected on to a vertical plane is less when the trunnion axis is inclined than when it is level, and therefore less than the angle corresponding to the range registered on the range dial or its equivalent, and the chief object of the present invention is to devise improved means for correcting this error.

According to this invention we provide means for automatically correcting the angle of tangent elevation by directly adjusting this angle, the amount of such correction being dependent upon the inclination of the gun trunnions and the range of the object.

When the invention is employed in conjunction with ordnance having an independent line of sight and in which the sight bracket is capable of being rocked about a longitudinal axis to bring it into a vertical position when the trunnions are inclined, we may employ a rotary cam with which a projection on the sight carrier cooperates.

In order that the said invention may be clearly understood and readily carried into effect we will describe the same more fully with reference to the accompanying drawings, in which Figures 1, 2 and 3 are respectively a side elevation a plan and a sectional rear elevation showing in a more or less diagrammatic manner a constructional form of the invention for directly varying the angle of tangent elevation.

In these figures A is one of the gun trunnions and B represents the aforesaid cam.

Referring to Figs. 1 to 3, C is the sight bracket which is capable of being rocked about a longitudinal axis a to bring it into the vertical position when the trunnions are inclined. D is the sight carrier and (Z represents the projection thereon for cooperating with the cam B. The arrangement of sighting apparatus shown in Figs. 1 to 3 is similar to that forming the subject of our British application for patent No. 631d of 1914 and need not therefore be particularly described.

The cam B, in the example shown, is rotatably mounted on the sight arm B (which moves only during the pointing opera-tion) near the rear end of the carrier D and is connected by a link D to an arm or bracket A on the gun trunnion A. This cam is so formed that when the sight bracket G is adjusted to the vertical position as aforesaid (assuming the gun to be already elevated for range) the sight carrier D will be rocked about a transverse pivot d (Fig. 1) to increase the angle between the sight line and the axis of the gun; and when the gun is being elevated for range (assuming the trunnions to be inclined and the sight bracket C to have been accordingly adjusted to a vertical position) the said cam will rock the sight carrier D in the opposite direction to the movement of elevation of the gun. When the trunnions are horizontal the projection cl on the carrier D will rest on a portion of the cam B which is concentric with the axis of rotation of the said cam so that no correcting movement will then be given to the carrier D during the ranging of the gun; when there is no angle between the sight line and the axis of the gun the proj ection d rests on a portion of the cam which is concentric with the axis 0 of the sight bracket so that in this case no correcting displacement will be given to the carrier D as a result of the ad ustment of the sight bracket C to its vertical position. The said cam is symmetrical on both sides of a vertical plane passing transversely through its center. It will therefore be seen that whether the bracket O, in being adjusted to its Vertical position, moves laterally toward or away from the axis of the gun, the cam B will effect the same correction in the angle of tangent elevation.

\Vhat we claim and desire to secure by Letters Patent of the United States is 1. In ordnance sighting apparatus, the combination with the sight carrier adapted to be adjusted about a longitudinal axis to its vertical position, of means for mounting said sight carrier to swing about a transverse axis, and means for automatically acting upon the sight carrier during the movement of the same to its vertical position to shift the carrier about its transverse axis to correct the error in the angle of tangent elevation due to the inclination of the gun trunnions.

2. In ordnance sighting apparatus, the combination with the sight carrier adapted to be adjusted about a longitudinal axis to its vertical position, of means for mounting said sight carrier to swing about a transverse axis, means for automatically acting upon the carrier during the movement of the same to its vertical position to shift the carrier about its transverse axis to correct the error in the angle of tangent elevation due to the inclination of the gun trunnions, and means operatggl by yert,cal niovementmomlna g un @iit its trunnions to move the last-named meanTshiid thereby slii'ft said carrier about its transverse axis to vary in accordance with the range of the target the above-mentioned correction to the error in the angle of tangent elevation.

3. In ordnance sighting apparatus, the combination with the sight carrier adapted to be adjusted about a longitudinal axis to its vertical position, of means for mounting said sight carrier to swing about a transverse axis, and means automatically operable both when the sight carrier is shifted to its vertical position about said longitudinal axis and when the gun is shifted in a vertical direction about the axis of its trunnions to shift said sight carrier about its transverse axis to correct the error in the angle of tangent elevation due to the inclination of the gun trunnions.

4. In ordnance sighting apparatus, the combination with the sight carrier, of a cam, and means for effecting relative movement in two planes between said cam and carrier for correcting the angle of tangent elevation for the error resulting from lack of level of the gun trunnions.

5. In ordnance sighting apparatus, the combination with the sight carrier and the sight bracket on which said carrier is mounted, of a cam, a projection on the sight carrier in contact with said cam, means for laterally adjusting said bracket to a vertical position when the gun trunnions are inclined during which adjustment the projection on the sight carrier moves over the cam and the angle of tangent elevation is thereby corrected for the degree of inclination of the gun trunnions, and means for angularly displacing said cam during the ranging adjustment so that the correction given to the angle of tangent elevation is varied in accordance with the range.

6. In ordnance sighting apparatus having an independent line of sight, the combination with the sight carrier and the sight bracket on which said carrier is mounted, of a member moving only during the pointing of the gun, a rotary cam carried by said member, a projection on the sight carrier in contact with said cam, means for laterally adjusting said bracket to a. vertical position when the gun trunnions are inclined, during which adjustment the projection on the sight carrier moves over the cam and the angle of tangent elevation is thereby corrected for the degree of inclination of the gun trunnions, and means for connecting said cam to the gun so that rotary movement of the cam occurs during the ranging of the gun, the correction of the angle of tangent elevation being thereby varied in accordance with the range.

In testimony whereof we affix our signatures in the )resence of two witnesses.

ARTI-I IR TREVOR DAWSON. GEORGE THOMAS BUOKHAM. Witnesses J NO. R. OAswnLL, GLADYS M. BARDEN.

copies of this patent may be obtained for five cents each, by addressing the Commissioner of Patents. Washington, D. 0. 

